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[TenTec] Crystal vs. DSP Filtering

To: tentec@contesting.com
Subject: [TenTec] Crystal vs. DSP Filtering
From: John Pfeifer <jpfeifer@gci.net>
Reply-to: tentec@contesting.com
Date: Tue, 02 Dec 2003 06:36:30 -0900
List-post: <mailto:tentec@contesting.com>
Hello all,

I've been playing around with my Omni V.9 in some QRP contests lately where I 
am trying to pick out one weak signal from a bunch of  weak signals.  
Everybody's running QRP and nobody is above S5.  When I crank in any filtering 
below 1.8 kHz, however, all of the signals are attenuated to the point that I 
can't hear anything.  I've noticed the same phenomena with my Elecraft K1 as 
well.  It seems like narrow filtering only works for signals that are S6 and 
above.

Is this simply a function of crystal filtering?  Is there always some 
attenuation occuring inside the passband? 

If so, do rigs with DSP filtering like the Argo V and Pegasus/Jupiter do better 
with weak signals when narrow filters are used?

BTW, I also notice that when I'm not using filters, it seems easier to pick out 
weak CW signals when you are tuned further off frequency and the resulting tone 
is higher.

Thanks,

John Pfeifer - KL0WN
Kodiak, Alaska


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